Gilles de la Tourette's Syndrome is a complex neuropsychiatric disorder which is thought to be due to some abnormality of neurotransmitter function. Several different neurotransmitter systems have been implicated in the disorder including dopamine, norepinephrine and serotonin. Several studies of the neuropsychological and electroencephalographic characteristics of Tourette's Syndrome patients have found a high frequency of abnormalities, although in most cases the abnormalities have been nonspecific. Very little is known about the relationship of symptom type or severity with brain chemistry of electrical activity. One major goal of the proposed research is to investigate the relationship of biochemical, behavioral and electrophysiological indices among each other, and also to a measure of Tourette symptoms. This will provide some insight into the pathophysiological mechanisms underlying these symptoms. In addition, a major focus of this research will be in the identification of subtypes. Numerous lines of evidence suggest that subgroups may exist in relation to family history, treatment response, associated psychopathology, or other factors. This research will establish the identity of those groups as well as the behavioral, biochemical and EEG characteristics. The identification of subgroups will have important implications for treatment, because different treatment regimens may be suggested by different biochemical or physiological substrate. The study will be based on comparison of a large group of Tourette Syndrome patients (200) and controls matched for age, sex, education, and socioeconomic status. The inter-relationships of the EEG, behavioral and biochemical data will be examined and compared with controls. Subgroups will be examined with cluster analytic techniques, and by forming groups based on historical subject characteristics. These groups will then be compared on the various types of data to determine the subgroup specific characteristics, ultimately forming the basis for specific treatment protocols.